Millimeter-Wave Cellular Wireless Networks: Potentials and Challenges
05 Feb 2014-Vol. 102, Iss: 3, pp 366-385
TL;DR: Measurements and capacity studies are surveyed to assess mmW technology with a focus on small cell deployments in urban environments and it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities.
Abstract: Millimeter-wave (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multielement antenna arrays. This paper surveys measurements and capacity studies to assess this technology with a focus on small cell deployments in urban environments. The conclusions are extremely encouraging; measurements in New York City at 28 and 73 GHz demonstrate that, even in an urban canyon environment, significant non-line-of-sight (NLOS) outdoor, street-level coverage is possible up to approximately 200 m from a potential low-power microcell or picocell base station. In addition, based on statistical channel models from these measurements, it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities. Cellular systems, however, will need to be significantly redesigned to fully achieve these gains. Specifically, the requirement of highly directional and adaptive transmissions, directional isolation between links, and significant possibilities of outage have strong implications on multiple access, channel structure, synchronization, and receiver design. To address these challenges, the paper discusses how various technologies including adaptive beamforming, multihop relaying, heterogeneous network architectures, and carrier aggregation can be leveraged in the mmW context.
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TL;DR: This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.
Abstract: What will 5G be? What it will not be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.
7,139 citations
Cites background from "Millimeter-Wave Cellular Wireless N..."
...Marzetta was instrumental in articulating a vision in which the number of antennas increased by more than an order of magnitude, first in a 2007 presentation [89] with the details formalized in a landmark paper [90]....
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TL;DR: This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.
Abstract: Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.
2,380 citations
Cites background from "Millimeter-Wave Cellular Wireless N..."
...A major outstanding issue is characterizing the joint probabilities in outage between links from different cells, which is critical in assessing the benefits of macro-diversity [65], [66]....
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TL;DR: Detailed spatial statistical models of the channels are derived and it is found that, even in highly non-line-of-sight environments, strong signals can be detected 100-200 m from potential cell sites, potentially with multiple clusters to support spatial multiplexing.
Abstract: With the severe spectrum shortage in conventional cellular bands, millimeter wave (mmW) frequencies between 30 and 300 GHz have been attracting growing attention as a possible candidate for next-generation micro- and picocellular wireless networks. The mmW bands offer orders of magnitude greater spectrum than current cellular allocations and enable very high-dimensional antenna arrays for further gains via beamforming and spatial multiplexing. This paper uses recent real-world measurements at 28 and 73 GHz in New York, NY, USA, to derive detailed spatial statistical models of the channels and uses these models to provide a realistic assessment of mmW micro- and picocellular networks in a dense urban deployment. Statistical models are derived for key channel parameters, including the path loss, number of spatial clusters, angular dispersion, and outage. It is found that, even in highly non-line-of-sight environments, strong signals can be detected 100-200 m from potential cell sites, potentially with multiple clusters to support spatial multiplexing. Moreover, a system simulation based on the models predicts that mmW systems can offer an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks with no increase in cell density from current urban deployments.
2,102 citations
Cites background from "Millimeter-Wave Cellular Wireless N..."
...It should be noted that the capacity numbers reported in [9], which were based on an earlier version...
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...widths are much wider than today’s cellular networks [4]–[9]....
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TL;DR: An overview of 5G research, standardization trials, and deployment challenges is provided, with research test beds delivering promising performance but pre-commercial trials lagging behind the desired 5G targets.
Abstract: There is considerable pressure to define the key requirements of 5G, develop 5G standards, and perform technology trials as quickly as possible. Normally, these activities are best done in series but there is a desire to complete these tasks in parallel so that commercial deployments of 5G can begin by 2020. 5G will not be an incremental improvement over its predecessors; it aims to be a revolutionary leap forward in terms of data rates, latency, massive connectivity, network reliability, and energy efficiency. These capabilities are targeted at realizing high-speed connectivity, the Internet of Things, augmented virtual reality, the tactile internet, and so on. The requirements of 5G are expected to be met by new spectrum in the microwave bands (3.3-4.2 GHz), and utilizing large bandwidths available in mm-wave bands, increasing spatial degrees of freedom via large antenna arrays and 3-D MIMO, network densification, and new waveforms that provide scalability and flexibility to meet the varying demands of 5G services. Unlike the one size fits all 4G core networks, the 5G core network must be flexible and adaptable and is expected to simultaneously provide optimized support for the diverse 5G use case categories. In this paper, we provide an overview of 5G research, standardization trials, and deployment challenges. Due to the enormous scope of 5G systems, it is necessary to provide some direction in a tutorial article, and in this overview, the focus is largely user centric, rather than device centric. In addition to surveying the state of play in the area, we identify leading technologies, evaluating their strengths and weaknesses, and outline the key challenges ahead, with research test beds delivering promising performance but pre-commercial trials lagging behind the desired 5G targets.
1,659 citations
TL;DR: Experimental measurements and empirically-based propagation channel models for the 28, 38, 60, and 73 GHz mmWave bands are presented, using a wideband sliding correlator channel sounder with steerable directional horn antennas at both the transmitter and receiver from 2011 to 2013.
Abstract: The relatively unused millimeter-wave (mmWave) spectrum offers excellent opportunities to increase mobile capacity due to the enormous amount of available raw bandwidth. This paper presents experimental measurements and empirically-based propagation channel models for the 28, 38, 60, and 73 GHz mmWave bands, using a wideband sliding correlator channel sounder with steerable directional horn antennas at both the transmitter and receiver from 2011 to 2013. More than 15,000 power delay profiles were measured across the mmWave bands to yield directional and omnidirectional path loss models, temporal and spatial channel models, and outage probabilities. Models presented here offer side-by-side comparisons of propagation characteristics over a wide range of mmWave bands, and the results and models are useful for the research and standardization process of future mmWave systems. Directional and omnidirectional path loss models with respect to a 1 m close-in free space reference distance over a wide range of mmWave frequencies and scenarios using directional antennas in real-world environments are provided herein, and are shown to simplify mmWave path loss models, while allowing researchers to globally compare and standardize path loss parameters for emerging mmWave wireless networks. A new channel impulse response modeling framework, shown to agree with extensive mmWave measurements over several bands, is presented for use in link-layer simulations, using the observed fact that spatial lobes contain multipath energy that arrives at many different propagation time intervals. The results presented here may assist researchers in analyzing and simulating the performance of next-generation mmWave wireless networks that will rely on adaptive antennas and multiple-input and multiple-output (MIMO) antenna systems.
1,417 citations
Cites methods from "Millimeter-Wave Cellular Wireless N..."
...The floating intercept model parameters for the 28 and 73 GHz campaigns are slightly different here than those described in [40], due to an updated PDP thresholding algorithm that uses a more stringent 5 dB SNR threshold, and by separating the TX-RX path loss data points by RX antenna...
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...A more detailed description of how the directional measurements were aggregated together to create omnidirectional models similar to those in [39] and [40] was presented in [38]....
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References
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01 Jun 2014
TL;DR: In this paper, beamforming and beam combining schemes using frequency domain equalization were proposed to reduce the path loss by coherently combining the four strongest beams at different pointing angles when compared to randomly pointed single beam antennas.
Abstract: Millimeter wave mobile systems equipped with adaptive antennas show tremendous potential to provide much higher data rates than traditional cellular systems while offering comparable signal quality. This article presents channel measurement results obtained using a spread spectrum sliding correlator channel sounder at 28 GHz with an ultra-wide RF first null-to-null bandwidth of 800 MHz, collected in the dense urban environment of New York City. Statistics of multipath components, RMS delay spread, path loss, and angle distributions are investigated for antennas with different beamwidths. Theoretical beam combining analysis is performed, showing that the path loss can be reduced by 18.7 dB/decade in distance by coherently combining the four strongest beams at different pointing angles when compared to randomly pointed single beam antennas. Preliminary designs of beamforming and beam combining schemes using frequency domain equalization are proposed.
37 citations
01 Jan 2012
TL;DR: In this paper, the challenges with and motivations for developing millimeter wave and terahertz communications are described, and a high-level candidate architecture is presented, and use cases highlighting the potential applicability of high-frequency links are discussed.
Abstract: In this paper, the challenges with and motivations for developing millimeter wave and terahertz communications are described. A high-level candidate architecture is presented, and use cases highlighting the potential applicability of high-frequency links are discussed. Mobility challenges at these higher frequencies are also discussed. Difficulties that arise as a result of high carrier frequencies and higher path loss can be overcome by practical, higher-gain antennas that have the added benefit of reducing intercell interference. Simulation methodology and results are given. The results show that millimeter wave coverage is possible in large, outdoor spaces, and only a reasonable number of base stations are needed. Network throughput can exceed 25 Gbit/s, and cell-edge user throughput can reach approximately 100 Mbit/s.
37 citations
01 Dec 2012
TL;DR: This paper investigates the use of analog multitone for sidestepping the ADC bottleneck: transmissions are split into a number of subbands, each of which can be separately sampled at the receiver using a lower rate ADC.
Abstract: Commercial exploitation of the large amounts of unlicensed spectrum available at 60 GHz requires that we take advantage of the low-cost digital signal processing (DSP) made available by Moore's law. A key bottleneck, however, is the cost and power consumption of high-precision analog-to-digital converters (ADCs) at the multiGigabit rates of interest in this band. This makes it difficult, for example, to apply traditional DSP-based approaches to channel dispersion compensation such as time domain equalization or Orthogonal Frequency Division Multiplexing (OFDM), since these are predicated on the availability of full-rate, high-precision samples. In this paper, we investigate the use of analog multitone for sidestepping the ADC bottleneck: transmissions are split into a number of subbands, each of which can be separately sampled at the receiver using a lower rate ADC. For efficient use of spectrum, we do not allow guard bands between adjacent subbands, hence the receiver signal processing must account for intercarrier interference (ICI) across subbands as well as intersymbol interference (ISI) within a subband due to channel dispersion. We illustrate our ideas for short-range (100–200 meters), highly directional, outdoor 60 GHz links, as might be employed for wireless backhaul. Given the large coherence bandwidth of the sparse multipath channels typical of such links that we consider, reliable performance requires spatial diversity, in addition to the beamforming required to close the link. We therefore consider one transmit and two receive antenna arrays, each with 4 × 4 elements. We investigate linear equalization strategies corresponding to different combinations of: (a) combining samples from both arrays/choosing the stronger array and (b) equalizing the subbands independently/jointly. We find that exploiting the spatial diversity completely by combining samples from both arrays is critical for combating fading and inter carrier interference.
29 citations
"Millimeter-Wave Cellular Wireless N..." refers background in this paper
...One promising route has been the use of compressed sensing and other advanced low-bit rate technologies, suggested in [97]....
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01 May 1994
TL;DR: The feasibility of using radio frequencies in the super high frequency (SHF) band (3-30 GHz) for Personal Communications Services (PCS) in buildings depends on the multipath within the structure and the amount of attenuation experienced by the electromagnetic waves passing through the structures.
Abstract: The feasibility of using radio frequencies in the super high frequency (SHF) band (3-30 GHz) for Personal Communications Services (PCS) in buildings depends on the multipath within the structure and the amount of attenuation experienced by the electromagnetic waves passing through the structures. This study measured these effects to obtain a quantitative estimate of the attenuation magnitude. This magnitude can then be used for link margin analysis to determine if personal communications at SHF is practical.
28 citations
"Millimeter-Wave Cellular Wireless N..." refers background in this paper
...For example, materials such as brick can attenuate signals by as much as 40–80 dB [8], [30], [56]–[58] and the human body itself can result in a 20–35-dB loss [59]....
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05 Jun 2011
TL;DR: In this paper, the authors used superposition and S-parameter techniques to de-embed the effects of probe tip radiation from measured on-chip antenna patterns performed in a probe station environment.
Abstract: We present two methods to remove wafer probe interference radiation from measured on-chip antenna patterns performed in a probe station environment. On-chip antenna pattern and gain measurements are affected by parasitic probe tip radiation as well as scattered energy from the metal probe station environment. In this work, we use superposition and S-parameter techniques to de-embed the effects of probe tip radiation. On-chip Dipole, Yagi, and Rhombic antennas were fabricated using standard 180nm CMOS, and radiation patterns were measured at 60 GHz. This work shows methods that improve the ability to reliably design, predict, and measure on-chip antenna patterns.
28 citations